This invention relates to a driving belt for continuous or stepless speed variation, and more particularly to a driving belt for stepless speed variation which is used for a belt-driven stepless speed change gear or the like.
A driving belt for stepless speed variation which has been conventionally known in the art is essentially constructed in such a manner as shown in FIG. 1. More particularly, the conventional driving belt for such a purpose generally includes a plurality of endless metal strips 100 laminated together and a plurality of plate-like carriers 102. The carriers 102 each are formed with a groove 104 through which the metal strips 100 are fittedly inserted. Also, each of the carriers 102 is provided on one side thereof in a direction of advance of the belt with a projection 106 and on the other side thereof with a recess 108 in a manner to positionally correspond to each other and mate in configuration with each other. Further, each of the carriers 102 is formed at a lower portion thereof with a tapered surface 110 so as to cause the lower portion to be downward tapered. The carriers 102 thus formed are so arranged that the projections 106 and recesses 108 are alternately fitted in order, resulting in being continuously arranged in a row on the endless metal strip 100.
The conventional driving belt constructed as described above is so operated that when each of the carriers 102 passes through a pulley, opposite surfaces of the carriers adjacent to each other which are contacted with each other start to be separated from each other, so that forward one of the adjacent carriers 102 in the direction of advance of the belt is pivotally moved about an upper end of the tapered surface 110 of the rearward carrier 102. This causes outer peripheral portions of the adjacent carriers 102 to be separated from each other, resulting in any displacement or deviation occurring in the engagement between the opposite projection 106 and recess 108 of the adjacent carriers 102 opposite to each other as shown in FIG. 1, so that interference readily occurs between the adjacent carriers. Also, this causes any slippage to occur between the carriers 102 and the metal strips 100, leading to generation of heat and wearing due to friction therebetween, so that power transmission through the driving belt is significantly deteriorated. It is a matter of course that clearance is provided between the metal strip 100 and the groove 104 and between the projection 106 and the recess 108. However, excessive clearance increases backlash of the carriers 102, to thereby cause the carriers to strike against the pulley to generate noise when they pass through the pulley; whereas insufficient clearance causes the carriers 210 to mesh with each other also in proximity to the pulley, resulting in a failure in rotation of the metal strips 100. Therefore, it is required to manufacture the carriers 102 with extremely high accuracy. Also, the clearance is increased with use to lead to the disadvantage indicated above.
Furthermore, the conventional driving belt requires to provide clearance sufficient to ensure rotation of the belt when a number of the carriers 102 are continuously arranged on the metal strips 100 in a longitudinal direction of the belt. Unfortunately, in this instance, a decrease in rotational speed of the pulley causes the clearance which is one-sided during rotation of the pulley to be varied to instantly generate backlash of the carriers 102, leading to vibration of the belt.